1.Field of the Invention
The present invention relates to an automatic document carrying device and, more particularly, to an image forming apparatus such as a copying machine having an automatic document carrying device.
2. Description of the Related Art
In a conventional copying machine, when a jam is detected by an automatic document carrying device, a copying unit is not supplied with a signal indicating where the jam occurs. Even though the jam is made at the intermediate position (which is referred to as a document forward-feeding position) between a paper feeding unit and an image forming position, the copying unit cannot detect whether the jam is a jam in document forward-feeding. Therefore, the copying unit interrupts its copying operation, regardless of where the jam occurs. More specifically, when a plurality of copies is made, the a copying operation is stopped before all of the copies are completed, and the remaining number of copies is stored in the copying unit. Then, the document is reset and the copying operation is restarted for the remaining number of copies.
When the jam in document forward-feeding occurs, the jammed document does not reach an exposure position (image forming position) and, thus, exercises no influence on a copy of another document at the exposure position. Nevertheless, a conventional copying machine stops its copying operation immediately and is, thus, inferior in operation. Further, since the copying operation is stopped before all the copies are competed, the copying unit has to store information indicating whether the remaining copies should be made or not, and a precise number of copies cannot be made unless the error in document forward-feeding is correctly handled.